Some banks will make you work longer hours than others. Some banks will pay you more than others. Some banks will work you long hours and then award you minimal compensation. These, you probably want to avoid.
As part of a new 'Emolument Employers' service, which allows users to compare pay at different firms, pay-benchmarking company Emolument.com has released the following chart showing average pay in the M&A divisions of various banks compared to the total fees earned in M&A transactions. Some banks (eg. Goldman Sachs) earn very high fees and pay comparatively small bonuses. Other banks (eg. UBS and Credit Suisse) pay comparatively high bonuses but earn tiny fees.
Assuming that M&A fees are a proxy for work done, the ranking below indicates which banks pay well relative to the amount of effort they require of their bankers. The implication is that Goldman, BAML and Morgan Stanley will all work you hard for minimal reward. UBS and Credit Suisse will work you less hard, but pay you nonetheless.
Naturally, there are caveats. Emolument's pay figures are based on data points from 1,077 directors. It's possible that the banks in question pay their analysts and associates differently. Equally, fees earned are not always indicative of hours worked. It's quite possible that M&A bankers at Credit Suisse and UBS are working very hard putting pitch-books together, but are failing to win deals on the back of them.
It's also worth remembering that it makes good career sense to work on a lot of live deals early in your career. Real execution experience can be more important than getting paid well. Tell yourself this if you're working for Goldman Sachs.